@andyp1984: Can you try pressing the Volume Down and Power buttons together for around 10 seconds until the phone restarts, as this will refresh your S20 FE and address any temporary issues that may be affecting the device. If the issue persists, can you confirm if the issue is affecting all contacts, or just certain ones? Do you have another compatible phone that you can try your SIM in to see if the problem remains, or another SIM that you can try in the S20 FE? Have you reached out to your network to enquire about any problems with their service in your area?
